1. Field of the Invention
The present invention relates generally to the field of devices that utilize optics, and more particularly to devices having an optical element wherein the optical element has a surface diffuser integral in one of the surfaces of the optical element to improve operation of the devices.
2. Description of the Related Art
There are many types of devices utilizing one or more optical elements such as Fresnel lenses, lenticular lenses, reflective surfaces, polarizers, fiber optics, cylindrical lenses, waveguide filters, grating structures, or other such optical elements. Such devices are useful in an ever growing number of applications. These devices typically utilize light from an ambient source or a beam or path of light from a source wherein the light passes through or hits the optical element in order to change one or more characteristics of the light. Examples of such devices include but are certainly not limited to medical diagnostic devices, illumination lamps, chemical analyzers, optical filters, LED displays and devices, LCD displays and devices, microscopes, spectroscopes, and even laser surgical devices. Each of these devices receives and utilizes light in one form or another and/or transmits light from the device in one form or another in performing its intended function.
All of these devices suffer from a number of deficiencies and disadvantages caused by the type and construction of their respective optical elements. Optical elements accomplish one or more inherent functions to change characteristics of light passing through or hitting the element. Such functions include transmission, reflection, diffraction, refraction, wavelength filtering, dispersion or spreading, collimating, and directing of light utilized by the device. performance of the optical elements is limited by the particular qualities of the source of light and its output characteristics. Such optical elements and hence their respective devices are not capable of substantially improving the quality of the light emanating from a source other than to perform their intended functions.
Each optical element within these devices receives, from a source, light having particular characteristics and then transmits and/or alters the light only as to the particular characteristics of the optical element. None of these devices or optical elements homogenizes the light to provide smooth, consistent light intensity, controls directionality of the light to eliminate scatter or wasted light, and shapes the light to produce a particular distribution shape or envelope.
For example, a fiber optic cable receives light energy at one end and, via a predetermined refractive index of the fiber core and cladding materials, continually and internally reflects the light as it passes through the fiber. Most of the light exits the fiber optic cable at another end in substantially the same form in which it was received (ignoring modal variations). Concave and convex lenses are used in many different applications such as film projectors, microscopes and telescopes to slightly bend light according to the amount of curvature or shape of the lenses and materials utilized to manufacture the lenses. A Fresnel lens includes a plurality of Fresnel optics or structures provided on the surface of the lens to refract light entering the lens in order to collimate and focus light as well as to crudely spread the light passing through the lens.
Many other optical elements are available which perform a particular optical function as well. Most optical elements are not capable of homogenizing or smoothing out the light intensity variations exiting an optical element. Additionally, most optical elements are not capable of controlling the directionality of light exiting the optical element. Also, most optical elements are not capable of defining a particular projected shape or light distribution pattern. No optical element has been capable of performing all three functions at the same time. Consequently, in many known optical elements, a significant amount of light is lost or wasted and, therefore, devices utilizing any such optical elements are also quite inefficient.
The assignee of the present invention has invented and patented diffuser sheets of material which can be applied as a separate layer to optical elements in order to add light homogenizing directing and shaping characteristics to the element. A laminate construction is thus formed including a sheet or layer of diffuser material applied or adhered to a surface of an optical element of a device. One problem with such a construction is that the sheet material is not very durable and may easily be damaged, scratched or otherwise deformed during use. Another problem with such a laminate construction is that the diffuser sheet material may simply peel away from the optical element over time or under some conditions. A more critical problem with such a laminate construction is that the mating surfaces between the two portions of the laminate create an interface that refracts or reflects a portion of light entering the optical element. This can cause a minimum loss of about 4% of the incident light at each mating surface. This light is therefore lost as either being reflected back into the optical element or refracted by the interface of the optical element. This phenomenon affects the efficiency and functioning of the device in which the optical element is installed.
A further problem with such a construction is that an index matching optical grade epoxy or adhesive must be used in order to adhere the two parts of the laminate together. The optical grade epoxy permits passage of light through itself but creates an additional unwanted refractive or reflective interface in the laminate. Hence, additional Fresnel losses, both between the diffuser layer and the epoxy as well as between the optical element and the epoxy are created in such a laminate construction. The epoxy layer also adds cost to the laminate construction as well as manufacturing complexity.
An additional problem with such an epoxy laminate optical element construction is that there are many instances where the epoxy is not fully and completely in contact with the two layers. Additionally, air bubbles can form in the epoxy or between the epoxy and one of the laminate layers caused by manufacturing process irregularities. Such problems within the epoxy further reduce the efficiency of the laminate construction by scattering, reflecting or refracting light passing within and through the optical element of a device. All of the above problems greatly reduce the performance and desirability of utilizing laminated optical elements within a device.
The assignee of the present invention has invented several ways of forming a micro-sculpted surface structure or a microstructure in various materials to form a surface diffuser on such materials. These methods are described in a number of issued patents and co-pending patent applications listed below. Many of these methods involve creating a master diffuser by exposing a photoresist material to a source of light and then replicating this master diffuser into one or more sub-masters of a more durable nature. There are also other methods of making replicas of a master diffuser which contain the optical features in the master. With some of these methods, the master diffuser is initially created optically. With others, it is created mechanically. Submasters are created from these master diffusers utilizing a number of methods whereby the master diffuser surface is replicated into a sub-master surface. These other methods are described in one or more pending U.S. applications, referenced below, which are assigned to the assignee of the present invention.
Commonly assigned U.S. patents and pending applications disclose related methods for making and recording optical products and replicating those products so that they may be mass produced. For example, U.S. Pat. No. 5,365,354 lentitled "Grin Type Diffuser Based on Volume Holographic Material," U.S. Pat. No. 5,534,386 entitled "Homogenizer Formed Using Coherent Light and a Holographic Diffuser," and U.S. Pat. No. 5,609,939 entitled "Viewing Screen Formed Using Coherent Light," all owned by the present assignee relate to methods for recording and replicating optical products. Each of these U.S. patents is incorporated herein by reference for purposes including, but not limited to, indicating the background of the present invention and illustrating the state of the art.
Related U.S. patent applications include Ser. No. 09/052,586 entitled "Method of Making Replicas While preserving Master," Ser. No. 08/595,307 entitled "LCD With Light Source Destructuring and Shaping Device," Ser. No. 08/601,133 entitled "Liquid Crystal Display System with Collimated Backlighting and Non-Lambertian Diffusing," Ser. No. 08/618,539 entitled"Method of Making Liquid Crystal Display System," Ser. No. 08/800,872 entitled "Method of Making Replicas and Compositions for Use Therewith," and Ser. No. 09/075,023 entitled "Method and Apparatus for Making Optical Masters Using Incoherent Light", "Non-Lambertian Glass Diffuser and Method of Making," filed Aug. 20, 1998, "Diffuser Master and Method of Manufacture," filed Aug. 20, 1998, "High Efficiency Monolithic Glass Light Shaping Diffuser and Method of Making," filed Aug. 25, 1998, "Optical Element Having an Integral Surface Diffuser," filed Aug. 25, 1998, "Apparatus Having a Light Source and a Sol-Gel Monolithic Diffuser," filed Aug. 25, 1998,"Passive Matrix Liquid Crystal Display," filed Aug. 25, 1998, and "Vehicle Light Assembly Including a Diffuser Surface Structure," filed Aug. 25, 1998. All the above applications are owned by the present assignee and are hereby incorporated by reference for purposes including, but not limited to, indicating the background of the present invention and illustrating the state of the art.